This invention relates to a slice lip applicable to a head box for a paper-making machine.
FIG. 1(a) shows an example of the slice lip at the tip of a conventional head box. The slice lip 1 is deflected in the Z-direction by means of a jack rod 2 with a pitch of about 150 mm and an interconnecting metal 3 so that the lip opening is changed. Thus, the flow rate in the direction of the width perpendicular to the surface of drawing is also changed and fine adjustment of the weight profile in the direction of the width is effected.
In this case, pressure is applied to a liquid-contacting surface, at A, of the slice lip 1 in order to obtain a jet J whereby the slice lip 1 is likely to be forced up and off a slice body 5. To prevent this displacement, a spring 6 is provided. However, reproducibility of the fine adjustment of the slice lip 1 in the direction of the width is low partly because the sliding frictional force of the slice body 5 is increased due to the force of this spring 6, partly because there is a relative slip between the slice lip 1 and the interconnecting metal 3, partly because the slice lip has bending rigidity in the direction of the width, and so forth.
Furthermore, since there is a corner formed at the joint surface or portion A, between the slice body 5 and the liquid-contacting surface of the slice lip 1, an unsteady flow is generated. This unsteady flow not only disturbs the jet J but also collects scum at the portion A.
In this case, such turbulence which occurs on the surface of the jet J, produces streaks and the like which eventually leads to a problem in the quality of products being formed. In FIG. 1(b), which shows in detail the portion X in FIG. 1(a), the error in the flatness of the surface K at the tip of the slice lip 1 results in the error in the lip opening and invites the non-uniformity of the jet J. The reference numeral 13 (FIG. 1(a) designates a wire or forming wire and the reference numeral 14 designates a forming roll.